1. Field of the Invention
The present invention generally relates to transmitting electrical current between rotating and translating bodies and, more particularly, but not by way of limitation, to a slip plate assembly including at least one draw unit for conductively supplying electrical current under rotational and translational force applications.
2. Description of the Related Art
A receiving system, such as for example electrical Christmas tree lights for use with a tree atop a rotating base, requires electrical current to be delivered from a power source to the receiving system via an electrical circuit path. For purposes of illustration, an electrocable may be provided for establishing an electrical circuit path from the power source to the receiving system. Unfortunately, if rotational forces are exerted on an electrocable, the electrocable often twists on itself or on the receiving system. In short, without integrating rotating electromechanical connectors with the electrocable, rotational forces often damage or destroy the electrical circuit path for transmitting electric current to the receiving system.
One solution typically includes connecting a slip ring and brush apparatus with an electrocable. With a sliding brush, a slip ring and brush apparatus transmits electrical current between relatively rotatable slip rings. Thus, as rotational forces from the electrocable rotate adjacent slip rings, an electrical circuit path is established between these slip rings through the sliding brush. However, because of frequent frictional wear between the slip rings and the brush, slip ring and brush apparatuses commonly provide a short operational life. Maintaining, repairing, and replacing brushes, brush holders, and slip rings associated with the slip ring and brush apparatuses often becomes a costly option.
Currently, slip ring and rolling contact apparatuses provides a cheaper alternative to a slip ring and brush apparatus. In effect, brushes are replaced with cheaper, electrically conductive rolling contacts. The rolling contacts roll within an annular space formed between adjacent and radially spaced rings. As rotational forces from an electrocable rotate the rings about a horizontal axis, the rolling contacts roll against the adjacent rings and conduct electrical current therebetween.
A shortcoming of the slip ring and roller bearing apparatus is that the electrical contact between adjacent slip rings and roller bearing cannot accommodate compressive- and tensile-translational forces exerted from the electrocable. Respectively, the pushing and pulling from the compressive-and tensile-translational forces may potentially damage or destroy an electrical circuit path for transmitting electric current to a receiving system. Inasmuch, translational forces disrupt the structural contact maintained and, thus, electrical contact between the slip rings and roller bearings. Although accounting for rotational forces, today""s slip ring and roller bearing apparatuses are not configured to also withstand translational force applications.
Accordingly, as a matter of reducing manufacturing time, labor, and cost, there is a long felt need for a slip plate assembly for supplying electrical current under rotational and translational force applications with built in contact wear compensation to maintain the flow of the electrical current as the contact wear.
In accordance with the present invention, a slip plate assembly for supplying electrical current under rotational and translational force applications, includes a housing and at least one drw unit, each draw unit disposed within the housing. The housing includes a lead wire and a return wire. The lead wire and return wires are each in electrical contact with the draw unit. In operation, each draw unit draws electric current from a power source, through an in-electrocable, across the lead wire to the draw unit. The draw unit then conducts and supplies electric current across the return wire, through an out-electrocable to a receiving system.
Optionally, in one exemplary embodiment, the housing may include shaft throughbore for receiving the in-electrocable therethrough as well as for facilitating any electrical connection of the in-electrocable with the lead wire. A mounting flange is further provided by the exemplary embodiment. The mounting shaft affixes to the end of a shaft or throughbore to permit the passage of a fiber optic rotary joint, a fluid or pneumatic swivel or any other object or device.
Each draw unit supplies electric current to the receiving system, as the receiving system and/or the in -and out-electrocables subject the draw unit to rotational and translational force applications. Each draw unit also includes a first electroplate and a second electroplate. Each draw unit includes a plurality of rolling members positioned within a gap formed between the first and second electroplates. While traversing this gap, each rolling member of the plurality of rolling members contacts the first and second electroplates. Therefore, in operation, an electrical circuit path is created between the first and second electroplates through each rolling member of the plurality of rolling members.
Each draw unit further includes a support spacer, positioned against the second electroplate, and a resilient element, positioned between the support spacer and the second electroplate. As the receiving system and/or the in-and out-electrocables subject each draw unit to rotational and translational forces, the resilient element resiliently supports the second electroplate. In effect, the support spacer is a stationary platform for enabling the resilient element to push the second plate and each rolling member of the plurality of rolling members against the first electroplate. Under rotational and translational forces, the resilient element ensures that the plurality of rolling members contact the first and second electroplates and, thus maintain the electrical circuit path between the first and second electroplates and through each rolling member.
Preferarbly, the draw unit further includes a guide notch disposed on each of the first and second electroplates. Each guide notch on the first and second electroplates then cooperate to define a track for the plurality of rolling members as the plurality of rolling members traverse the gap. Therefore, to ensure a desired position of a plurality of rolling members between a gap, a guide notch provides each first and second electroplates with increases surface area for physical or xe2x80x9cstructuralxe2x80x9d contact as well as electrical contact between that electroplate and each rolling member.
To further increase surface area along each guide notch, the plurality of rolling elements are preferably harder than each of the first and second electroplates. As they traverse the gap, the plurality of rolling elements wear against the first and second electroplates to increase surface area for contact between each rolling member and the first and second electroplates. Optionally, to still further increase electrical contact, a conductive coating is deposited on the first and second electroplates about each guide notch.
To protect the slip plate assembly from external environmental factors, the slip plate assembly may be sealed within a housing.
It is therefore an intent of the present invention to provide a slip plate assembly including at least one draw unit for conductively supplying electrical current under rotational and translational force applications.
Still other intentions, objects, features, and advantages of the present invention will become evident to those skilled in the art in light of the following.